Cell Cycle & MitosisCell Cycle & MitosisMs. LevensailorMs. Levensailor

Plan for understanding the cell Plan for understanding the cell cyclecycle

Establish important vocabulary.Establish important vocabulary. Develop an understanding of the overall Develop an understanding of the overall

process.process. Dive into the details of the mitotic cell Dive into the details of the mitotic cell

cycle.cycle. Know what is happening at each step.Know what is happening at each step. Identify significant features of the cell during Identify significant features of the cell during

each step.each step.

Cell Division FunctionsCell Division Functions

Reproduction: asexual and sexualReproduction: asexual and sexual Growth & Development: fertilized eggGrowth & Development: fertilized egg Tissue renewal: repair and replacing cells Tissue renewal: repair and replacing cells

that diethat die Involves the distribution of Involves the distribution of identicalidentical

genetic material (DNA) to 2 daughter cells.genetic material (DNA) to 2 daughter cells.

Cell DivisionCell Division GenomeGenome: a cells DNA (genetic information).: a cells DNA (genetic information). Eukaryotic genomes are enormous.Eukaryotic genomes are enormous. DNA is packaged into chromosomes.DNA is packaged into chromosomes.

This packaging makes replication manageable within This packaging makes replication manageable within the cell.the cell.

Eukaryotes have a set number of chromosomes Eukaryotes have a set number of chromosomes in each cell nucleus.in each cell nucleus. Human Human somatic cellssomatic cells (body cells not including (body cells not including

reproductive cells) contain reproductive cells) contain 46 chromosomes46 chromosomes..

Eukaryote ChromosomesEukaryote Chromosomes

Cell DivisionCell Division

Each chromosome is one very long, linear Each chromosome is one very long, linear DNA molecule.DNA molecule. Represents thousands of Represents thousands of genes genes (an (an

organisms inherited traits).organisms inherited traits). DNA is associated with proteins that maintain DNA is associated with proteins that maintain

the structure of the chromosomes.the structure of the chromosomes. ChromatinChromatin: DNA-protein complex.: DNA-protein complex. Organized into a long thin fiber.Organized into a long thin fiber.

ChromatinChromatin

After DNA is duplicated for division, After DNA is duplicated for division, chromatin is condensed!chromatin is condensed! It becomes densely folded and coiled.It becomes densely folded and coiled. We can now see it using a light microscope.We can now see it using a light microscope.

Sister ChromatidsSister Chromatids Each duplicated chromosome has 2 Each duplicated chromosome has 2 sister sister

chromatids.chromatids. Contain identical copies of the chromosome’s Contain identical copies of the chromosome’s

DNA molecule.DNA molecule. CentromereCentromere: narrow waist of the : narrow waist of the

chromosome.chromosome. Pulled apart and repackaged as complete Pulled apart and repackaged as complete

chromosome sets.chromosome sets. In 2 new nuclei, one at each end of the cell.In 2 new nuclei, one at each end of the cell.

MitosisMitosis

MitosisMitosis: division of the nucleus.: division of the nucleus. Followed by Followed by cytokinesis.cytokinesis.

CytokinesisCytokinesis: division of the cytoplasm.: division of the cytoplasm.

Details of the Cell CycleDetails of the Cell Cycle

2 main phases:2 main phases: InterphaseInterphase: :

Accounts for 90% of the cycle.Accounts for 90% of the cycle. Cell grows and copies chromosomes in prep for Cell grows and copies chromosomes in prep for

division.division. Mitotic phaseMitotic phase::

Includes mitosis and cytokinesis.Includes mitosis and cytokinesis. Shortest part of cell cycle.Shortest part of cell cycle.

Details of the Cell CycleDetails of the Cell Cycle

InterphaseInterphase Divided into subphases:Divided into subphases:

G1 phaseG1 phase (first gap): (first gap): S phase S phase (synthesis of DNA): Chromosomes (synthesis of DNA): Chromosomes

are duplicated!are duplicated! G2 phase G2 phase (second gap):(second gap):

During all 3 phases cell is growing by During all 3 phases cell is growing by producing proteins and cytoplasmic producing proteins and cytoplasmic organelles.organelles.

*NOTE: Fill in graphic organizer!*NOTE: Fill in graphic organizer!

InterphaseInterphase

Nucleus is well defined and bound by the Nucleus is well defined and bound by the nuclear envelope.nuclear envelope.

2 2 centrosomescentrosomes are outside the nucleus. are outside the nucleus. Features a pair of Features a pair of centriolescentrioles (animal cells (animal cells

only).only). AstersAsters: microtubules extend from the : microtubules extend from the

centrosomes in radial arrays.centrosomes in radial arrays.

InterphaseInterphase

Onion root tip

MitosisMitosis

Broken up into 5 main subphases:Broken up into 5 main subphases: ProphaseProphase PrometaphasePrometaphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

ProphaseProphase

Changes in the nucleus:Changes in the nucleus: Chromatin fibers become more tightly coiled.Chromatin fibers become more tightly coiled.

Condense into discrete chromosomes.Condense into discrete chromosomes. Chromosomes appear as 2 sister chromatids.Chromosomes appear as 2 sister chromatids.

Nucleoli disappear.Nucleoli disappear. Changes in the cytoplasm:Changes in the cytoplasm:

Mitotic spindle forms (made of microtubules).Mitotic spindle forms (made of microtubules). Centrosomes move away from each other.Centrosomes move away from each other.

PrometaphasePrometaphase

Nuclear envelope fragments.Nuclear envelope fragments. Microtubules interact with the Microtubules interact with the

chromosomes:chromosomes: Bundles of microtubules extend from each Bundles of microtubules extend from each

pole and toward the middle of the cell.pole and toward the middle of the cell. Each of the chromatids has a Each of the chromatids has a kinetochorekinetochore..

Located at the centromere.Located at the centromere. Microtubules attach at the kinetochore.Microtubules attach at the kinetochore.

ProphaseProphase

Onion root tip

MetaphaseMetaphase Centrosomes are at opposite poles of the cell.Centrosomes are at opposite poles of the cell. Chromosomes line up on the Chromosomes line up on the metaphase platemetaphase plate..

Imaginary plane that is equidistant between the 2 Imaginary plane that is equidistant between the 2 poles.poles.

Kinetochores are attached to microtubules of the Kinetochores are attached to microtubules of the opposite pole.opposite pole.

SpindleSpindle is formed. is formed. Entire apparatus of microtubules.Entire apparatus of microtubules.

MetaphaseMetaphase

AnaphaseAnaphase

Paired centromeres of each chromosome Paired centromeres of each chromosome separate.separate. Frees sister chromatids from each other.Frees sister chromatids from each other. Now considered chromosomes.Now considered chromosomes.

Chromosomes move toward opposite Chromosomes move toward opposite poles.poles. Result of kinetochore microtubules.Result of kinetochore microtubules.

AnaphaseAnaphase

TelophaseTelophase

Daughter nuclei form at the two poles of Daughter nuclei form at the two poles of the cell.the cell.

Nuclear envelope forms (from parent cell).Nuclear envelope forms (from parent cell). Chromatin fiber of each chromosome Chromatin fiber of each chromosome

becomes less tightly coiled.becomes less tightly coiled. Mitosis is complete!Mitosis is complete!

The division of one nucleus into 2 genetically The division of one nucleus into 2 genetically identical nuclei.identical nuclei.

TelophaseTelophase

CytokinesisCytokinesis Division of the cytoplasm.Division of the cytoplasm. 2 daughter cells appear at the end of 2 daughter cells appear at the end of

mitosis.mitosis. In animal cells cytokinesis involves:In animal cells cytokinesis involves:

Formation of a cleavage furrow.Formation of a cleavage furrow. Pinching the cell in 2.Pinching the cell in 2.

In plant cells:In plant cells: No cleavage furrow.No cleavage furrow. Produce a cell plate.Produce a cell plate.

Cytokinesis in AnimalsCytokinesis in Animals

Cytokinesis in PlantsCytokinesis in Plants

During telophase:During telophase: Vesicles from the golgi apparatus move along Vesicles from the golgi apparatus move along

microtubules to the middle of the cell.microtubules to the middle of the cell. This produces a This produces a cell platecell plate.. Cell wall materials carried in the vesicles Cell wall materials carried in the vesicles

collect in the cell plate.collect in the cell plate. Cell plate enlarges and fuses with the plasma Cell plate enlarges and fuses with the plasma

membrane.membrane. Results in 2 daughter cells.Results in 2 daughter cells.

Cytokinesis in PlantsCytokinesis in Plants

Mitotic SpindleMitotic Spindle Mitosis is dependent on the mitotic Mitosis is dependent on the mitotic

spindle!spindle! Consists of fibers made of microtubules Consists of fibers made of microtubules

and associated proteins.and associated proteins. Interesting note: while mitotic spindle is Interesting note: while mitotic spindle is

forming the microtubules of the forming the microtubules of the cytoskeleton disassemble.cytoskeleton disassemble.

Microtubules elongate by subunits of the Microtubules elongate by subunits of the protein tubulin (does this sound familiar?). protein tubulin (does this sound familiar?).

Regulation of the Cell CycleRegulation of the Cell Cycle

Brainstorm with a neighbor:Brainstorm with a neighbor: What controls/regulates the cell cycle?What controls/regulates the cell cycle? Possibilities if there are errors in this system.Possibilities if there are errors in this system.

Molecular Control SystemMolecular Control System

Cell cycle is driven by specific chemical Cell cycle is driven by specific chemical signals present in the cytoplasm.signals present in the cytoplasm. Cell Cycle Control SystemCell Cycle Control System

Cell cycle is regulated at 3 checkpoints by Cell cycle is regulated at 3 checkpoints by both internal and external controls.both internal and external controls. G1G1 G2G2 MM

Checkpoint LocationsCheckpoint Locations

CheckpointsCheckpoints

Stop and go signals regulate cell cycle.Stop and go signals regulate cell cycle. Signals report whether crucial cellular Signals report whether crucial cellular

processes have been completed correctly.processes have been completed correctly. G1 Checkpoint- “Restriction Point”G1 Checkpoint- “Restriction Point”

Once past this point, cell will complete the cell Once past this point, cell will complete the cell cycle.cycle.

If not, exit cell cycle to non-dividing state- “G0 If not, exit cell cycle to non-dividing state- “G0 Phase”Phase”

Checking for. . .?Checking for. . .?

Cell Cycle ClockCell Cycle Clock

Regulatory molecules are proteinsRegulatory molecules are proteins KinaseKinase: enzymes that activate or inactivate : enzymes that activate or inactivate

other proteins by phosphorylation.other proteins by phosphorylation. Present at a constant concentration in a growing Present at a constant concentration in a growing

cell.cell. Mostly in an inactive form.Mostly in an inactive form. Activated by cyclin. (Activated by cyclin. (Cyclin Dependent KinasesCyclin Dependent Kinases))

Cyclin: protein that fluctuates in concentration Cyclin: protein that fluctuates in concentration in the cell.in the cell.

Cell Cycle ClockCell Cycle Clock

Abnormal Cell Division Abnormal Cell Division Cancer cells do not respond to the body’s Cancer cells do not respond to the body’s

control mechanisms.control mechanisms. They ignore: They ignore:

Density-dependent inhibition: crowded cells stop Density-dependent inhibition: crowded cells stop dividing.dividing.

Anchorage dependence: cells must be attached to a Anchorage dependence: cells must be attached to a substratum.substratum.

Cell cycle checkpoints.Cell cycle checkpoints. Can divide indefinitely with a continual supply Can divide indefinitely with a continual supply

of nutrients.of nutrients. ““immortal”immortal”

Impacts on the BodyImpacts on the Body

Cancer cells are “Cancer cells are “transformed celltransformed cells”- s”- conversion from normal to cancer cell.conversion from normal to cancer cell.

Normally the immune system would destroy Normally the immune system would destroy these cells.these cells.

If a transformed cell survives it will form a If a transformed cell survives it will form a tumortumor: a mass of transformed cells.: a mass of transformed cells. Benign if it stays in its original site.Benign if it stays in its original site. Malignant if it spreads to other parts of the body.Malignant if it spreads to other parts of the body.

Spreading MechanismSpreading Mechanism

Cancer cells lose their attachment to Cancer cells lose their attachment to neighboring cells.neighboring cells.

Can enter the blood and lymph vessel of Can enter the blood and lymph vessel of the circulatory system.the circulatory system.

They can now invade other parts of the They can now invade other parts of the body and form more tumors (metastasis).body and form more tumors (metastasis).

TreatmentTreatment

Benign tumors: Removed by surgery.Benign tumors: Removed by surgery. Radiation: therapy using high-energy Radiation: therapy using high-energy

radiation to shrink tumors and kill cancer radiation to shrink tumors and kill cancer cells.cells. Kills cancer cells by damaging their DNA Kills cancer cells by damaging their DNA Cancer cells whose DNA is damaged beyond Cancer cells whose DNA is damaged beyond

repair stop dividing or dierepair stop dividing or die

TreatmentTreatment

Chemotherapy: drugs that interfere with Chemotherapy: drugs that interfere with the ability of cancer cells to divide and the ability of cancer cells to divide and reproduce themselves. reproduce themselves. Delivered by the bloodstream to reach cancer Delivered by the bloodstream to reach cancer

cells all over the body.cells all over the body. How is treatment chosen?How is treatment chosen?

Based on type of cancer and location in the Based on type of cancer and location in the body.body.